Snap-action devices



Sept. 19, 1961 n. A. wlLsoN SNAP-ACTION DEVICES 2 Sheets-Sheet 1 Filed sept. s, 195e f y la@ 2 s 2 2 I l j/ Q, M@ 4 x 1 \I/ J! M, @Il 2 3 2z 5- z g 4. s w, a l l l 7 9/ n law/Z /fb M/m w.,

Sept. 19, 1961 D. A. wlLsoN 3,001,041

sNAP-AcTIoN DEVICES Filed Sept. I5, 1958 2 Sheets-Sheet 2 United States Patent() 3,001,041 SNAP-ACTION DEVlCES David Alexander Wilson, Sunderland, England, assigner to Burgess Products Company Limited, Hinckley, England, a company of Great Britain and Northern Ireland 'Filed Sept. 3, 1953, Ser. No. 758,825 Claims priority, application Great Britain Sept. 30, 1957 3 Claims. (Cl. 200-67) This invention relates to snap-action devices and more particularly to snap-action electric switches, including switches having rotary operating members, which are suitable for use in coin-operated devices.

The invention has for an object to provide a snapaction device of simple construction which has a long life, and which more particularly is operable by a very low rotary torque.

A snap-action device according to the invention comprises two spaced fixed stops, a substantially flat, rigid member having one end disposed between said stops and its other end pivotally engaged at a fixed abutment, a tension link including or comprising a coil spring anchored at one end to said ilat member remotely from said abutment, and at its other end to a fixed anchorage, a rotary operating cam or eccentric disposed to bear on one side of said tension linlk, and a unitary element alfording said fixed abutment and fixed anchorage and at least one bearing for a spindle of said cam or eccentric.

Preferably, the flat member is U-shaped or forked, with two parallel arms pivotally bearing by their ends in a common line on a pair of fixed abfutments, and a single tension link 'having one end anchored at the root of the fork extends lbetween said arms.

The arrangement is such that when the cam or eccentric does not bear upon the tension spring, the latter pulls the free end of the ilat memlbcr into engagement with one of the fixed stops, the points of anchorage of the tension link and the line of said pivotal abutment or abut-ments being in a triangle having a large obtuse angle (nearly 180) at said line, in a plane normal to said line. When the cam or eccentric is caused to bear upon the tension link, the latter is flexed and the axis of the portion of the link extending from the radius through the point of contact of the cam or eccentric with the link to the anchorage on the ilat member is caused to pass through a common plane including said last mentioned anchorage and said pivotal line, to form another shallow triangle, inverted with respect to the first, and again having a large obtuse angle at said pivotal line. During such displacement, the -free end of the flat member is caused to move with a snap-action from engagement with one of said fixed stops to engagement with the other. When the operating torque applied to the cam or eccentric is reduced, the tension of the extended, liexed spring serves to restore the switch to its initial state, turning the cam or eccentric back and causing the free end of `the flat member to move back with a snap-action between the fixed stops.

Said flat member may carry at its: free end either a single electrical contact, one of said fixed stops also being an electrical contact, so that the device forms a snapaction make-and-break switch, or said member may carry yan opposed pair of contacts, each fixed stop being an electrical contact, so that the device forms a snapaction changeover switch, the element affording the abutment for said flat member serving in each case as a terminal of the switch.

A snap-action device or switch mechanism as aforesaid may Ibe mounted on a base, for example a plastic moulding, having a substantially flat sur-face with respect to which said pivotal abutment iline is perpendicular and the ICC tension link lies parallel. Such a base may provide one bearing for the spindle of the cam or eccentric, or said unitary element may include a portion adjacent said surface of the base providing one such bearing and another, spaced parallel portion alording a second bearing.

Said unitary element may be a pressing of sheet metal, for example, of brass or a like alloy.

An embodiment of a switch `including a snap-action mechanism according to the invention and a modication will ybe described E'by way of example with reference to the accompanying drawings, all on an enlarged scale, wherein FIG. 1 is a front view of the switch with a cover mainly broken away to show the internal construction,

FIG. 2 is a section on the line A-A of FIG. l.

FIG. 3 is a view of a detail, seen in the direction of arrow B in FIG. 1,

FIG. 4 is a plan view of said detail,

FIG. 5 is a view of a flat blank from which said detail is Iformed, and

FIG. 6 is a View corresponding to FIG. l, partly in section, of a modication.

The embodiment of the invention comprises the combination of a snap-action mechanism, mounting means for said mechanism and three terminals (common, normal open and normal closed) in a change-over switch.

The switch 1 has an insulating base 2 with parallel flat surfaces at three levels which for convenience of description will be considered as being in vertical planes. The basic surface level may lbe considered as that of a middle portion 3: and a marginal shoulder 4, from which project a three-Sided nib 5 and two small lozenges 6 and 7 serving jointly to locate by their outer edges the rim 8 of a boxlke cover 9. Through diagonally opposed corners of the cover and the base are formed holes 10 by which said elements are secured together, as shown by tubular rivets 11.

There are also two depressions 12 and 13. The former serves to accommodate and locate by their upper righthand corners and adjacent top and side edges vertical tab portions 14 and 15 (which serve respectively as the common and normal open terminals of the switch) of the aforesaid unitary element 16 and of .another element 17. The depression 13 serves to accommodate and locate a vertical tab portion 18 (which serves as the normal closed terminal of the switch) of a third element 19. Each of these elements is scoured by a rivet 20.

The unitary element is a pressing of sheet brass, preferably silver plated, made from a blank as shown in FIG. 5, by bending to the form shown in FIGS. l-4 on the lines a-a, b-b and c-c. The tab 114 has at or adjacent its upper end a perpendicularly projecting arm 21 in a vertical plane with two spaced parallel upward extensions 22 having each one of two aligned, horizontal grooves 23 to serve as pivotal abutments. The tab also has another perpendicularly extending arm 24, lying in a horizontal plane which passes close to said grooves, and having in its side remote from said upward extensions a notch 25 to provide an anchorage for one end of a tension link constituted in this embodiment solely by `a coil spring 26 (FIG. 1).

The element also includes, between said `upward extensions and said notched arm, an upwardly extending tongue 27, in a plane parallel to that of the tab 14, which has a hole 28 to serve as a 4bearing 4for one end of a cam spindle, or preferably, as shown, an element of a cam and spindle assembly. This hole is shown aligned with a hole 29 in a bush or housing 30 secured in the base. In the preferred arrangement, as illustrated, said notched arm 24 is an integral part of an L-shaped prolongation 31 of the outer of said upward extensions 22, but down vinto a horizontal plane and having 'bent yup from the middle of the outer edge of its shank, and integral therewith, the aforesaid bearing tongue 27. This arrangement has the eiect that stress in the tension spring 26, which tends to pull said notched arm toIw-ards said upward extensions, is resisted Voy the shank of the L-shaped prolongation lying alongside the spring.

A substantially ilat member 32, having two paral-lel arms, is located substantially horizontally and held with the oblique bent ends 33` of the arms in engagement with the aforesaid abutment grooves 2&3 by the spring 26, estending between said arms and having one end 314 anchored to the flat memiber 32 at its crotch and the other end 35 anchored in said notch 2S. rihe bent ends 33 of the member L32 engage, as shown in FIG. 1, in the grooves 23 with an edge contact. The tip of the member 32 carries two electrical contacts 36, one on each side, and is located between a pair of iixed contacts, one contact 37 being constituted by a horizontal extension parallel to the base from and integral with the element 17, and the other Contact 38 by a horizontal extension, perpendicular to the base, from the element 19.

Mounted on a spindle 39, which is partly supported for angular displacement in the bush 30` secured in the base and extends perpendicularly to the base, is` an aceentric cam 40 of insulating material which receives one end of the spindle and is supported rotatably in the hole 2S in the tab 27. The cam is turnable with the spindle, and is adapted to bear when turned on the upper side of the tension coil spring 26 so as to deflect it and cause operation of the switch.

In the modication shown in FIG. 6` the tension link comprises a shorter coil spring 46, in alignment with a wire link 47. Said link has two downwardly hooked ends 48 and '49, the former engaging a hooked end 50 of the spring and the latter being anchored in the notch 25. The other hooked end 51 of the spring is anchored to the dat memiber 32 of its notch. 'The cam 40 bears` on the wire link 47 as shown. This arrangement has the effect of aiording a significant improvement in mechanical life of the mechanism, even as compared with that afforded by the arrangement wherein the cam bears on the side of a longer coil spring as shown in FIG. l.

On the outer side of the base the spindle has a boss il whereby it may he turned. Said boss may have attached to it means ladapted for displacement by a cam or a coinoperated mechanism in a pre-payment device. As described above, the inherent restoring force of the tension coil spring, when extended by flexing in e-ither of the arrangements illustrated, enables the mechanism after being operated by a unidirectional force to return to its initial state on reduction of said force.

For limiting the angular displacement of the cam there is mounted on the spindle 39 a disc i2 ywith a radial extension the end 43 of which is bent to form an axial ilange which is displaceable between abutments presented by the inner edge of the upper part of the rib and the inner edge of an arm 44 formed to extend inwardly from the side of said rib in the base moulding.

The cam 40 and its spindle 39 may alternatively be a unitary moulding for example of nylon plastic. The base may be a moulding of a suitable, e.g., phenolic, plastic.

There may be associated with the boss` 42 a wire operating anm formed at one end as a torsion spring with a tail which intersects the axial plane of said arm, such that said torsion spring may be opened Ifor location on ory removal from the spindle by pressing the arm and the tail together, whereby the arm may be located on the spindle in any desired or convenient angular relationship with the cam. Said operating arm may be lodged in a transverse slot 45 in the end of the boss.

What I claim and desire to secure by Letters Patent is:

l. In a snap-action switch comprising two spaced iixed stops of which at least one is an electrical contact, va substantially flat rigid member having one end disposed between said iixed stops, a iixed abutment which is engaged by the other end of said rigid member, at least one contact carried by said one end of said rigid member to be engageable with said iixed contact, a link resiiicntiy extensible under tension anchored at one end to said rigid member remotely from said abutment, aiixed anchorage to which the other end of said tension link is anchored, a rotary operating cam disposed to bear on one side or" said tension link, and a spindle with which said cam is assembled, the combination of a snap-action mechanism separable from the switch in sub-assembly, comprising said rigid member and said tension link with a unitary element aiording said fixed abutment for said rigid member, said iixed anchorage for said tension link, and at least one bearing for said carn-andspindle assembly.

2. In a snap-action switch, a snap-action mechanism as claimed in claim l, in which said unitary element comprises a metal sheet bent along three fold lines to form four flat members, of which a first one serves as a mounting plate and common terminal for said mechanism in the switch, a second one accommodates said iixed abutment, a third one accommodatessaid xed anchorage, and the fourth one accommodates said bearing.

3. In a switch, a snap-action mechanism as claimed in claim l, in which said tension link comprises a coil spring anchored at one of its ends to said rigid member remotely from said abut-ment, and a Wire link element having two hooked ends anchored by one of said ends to the other end of said coil spring and by the other of said ends to said fixed anchorage, said -cam and said wire link being disposed so that said cam bears on one side of said wire link.

References Cited in the file of this patent UNITED STATES PATENTS 1,746,674 Persons Feb. 11, 1930 1,784,207 Stevens Dec. 9, 1930 1,960,020 McGall May 22, 1934 2,573,588 Miller Oct. 30, 1951 2,758,171 Cherry Aug. 7, 1956 2,862,083 Bailey Nov. 25, 1958 FOREGN PATENTS 963,446 Germany May 9, 1957 

